Perfluoroaryl Grignard reagents are useful in the synthesis of metal and metalloid perfluoroaryl compounds. Many preparations of perfluoroaryl Grignard reagents are known in the literature, some of which call for stoichiometric amounts of Grignard reagent and the polyhaloaromatic compound, J. Organomet. Chem., 1969, 18, 263-274, and J. Organomet. Chem., 1968, 11, 619-622. Others describe the use of excess Grignard reagent, J. Org. Chem., 1964, 29, 2385-2389, and J. Organomet. Chem., 1969, 19, 191-195. While it will not be considered further here, it should be noted that perfluoroaryl Grignard reagents have been generated in which the perfluoroaryl Grignard reagent is made directly from Mg metal and the polyhaloaromatic compound, as reported in J. Chem. Soc., 1959, 166-171, and J. Org. Chem., 1964, 29, 2385-2389. Two U.S. patents describe methods for obtaining perfluoroaryl Grignard reagents, one with the Grignard reagent in excess, U.S. Pat. No. 5,362,423, and the other with the polyhaloaromatic compound in excess, U.S. Pat. No. 5,600,004.
Separation of unreacted alkyl Grignard reagent and polyhaloaromatic compound starting materials from the reaction mixture is often desired, due to their interference in subsequent syntheses, but such separation is not always feasible.